Autonomic nervous system and cardiovascular risk assessment during one year of growth hormone replacement therapy in adults with growth hormone deficiency.

Abstract

This prospective study aimed to evaluate the impact of growth hormone deficiency (GHD) on cardiac autonomic tone and on cardiovascular risk and the changes after 12 months of GH replacement therapy (GHRT). GHD is associated with increased cardiovascular morbidity and mortality. This has been attributed to increased markers of cardiovascular risk and to abnormalities of both the cardiac and peripheral autonomic nervous systems. The autonomic cardiac nervous system (ACNS) can be indirectly evaluated by analysis of heart rate variability (HRV) in clinostatism and orthostatism. We compared 14 GHD patients at baseline and after 12 months of GHRT and 17 healthy controls. We analyzed a number of cardiovascular risk factors and we used analysis of HRV during the Tilt Test that identified high frequency (HF) and low frequency (LF), representing parasympathetic and sympathetic activity, respectively. Compared with the control group, in either clinostatism or in orthostatism our patients showed a significantly lower value of LF (P=0.047; P=0.004, respectively), whereas HF was significantly reduced in orthostatism (P=0.037), and indicatively in clinostatism (P=0.065). These values remained unchanged after 12 months of GHRT. No statistically significant differences were found between the LF/HF ratio in untreated and treated patients. In GHD patients, there was a significant reduction of cardiovascular risk in 12 months of replacement therapy (P=0.002). Our study highlights the absence of sympathovagal imbalance in GHD patients; GHRT does not change ACNS during the first year of GH treatment but it reduces the absolute cardiovascular risk in these patients.